Brush-seal and matrix for regenerative heat exchanger, and method of adjusting same

ABSTRACT

Disclosed is a regenerative heat exchanger including a brush-seal configuration to prevent mixing of fluid flows. The regenerative heat exchanger includes a regenerator, and at least two conduits, each conduit having a matrix end abutting a face of the regenerator matrix. The at least two conduits carrying at least two fluid flows, the fluid flows which pass through the regenerator matrix. The regenerative heat exchanger includes a plurality of brush-seals, each brush-seal located at a matrix end of each conduit without contacting the matrix, thereby sealing around a periphery of each conduit to prevent mixing of fluid flows. Also disclosed is a method for establishing a minimal gap between a regenerator matrix of a regenerative heat exchanger and a plurality of brush-seals.

BACKGROUND OF THE INVENTION

This invention generally relates to heat exchangers. In particular, thepresent invention relates to seals for rotary regenerative heatexchangers.

A regenerative heat exchanger (regenerator) uses a heat transfer matrixwhich is rotated through a hot and a cold stream consecutively totransfer heat from the former to the latter. The device call also beused to transfer mass between two fluids differing in concentration in atargeted constituent and the exchange (be it mass and/or heat) caninvolve any number of flows greater than one.

Each of the hot and cold flows is typically carried to and from thematrix by a conduit. The flows enter and exit the matrix through a faceof the matrix, and a configuration of seals is located between theconduits and the rotating matrix face to prevent leakage of the flowsfrom the conduits into the environment or from one flow into another.Two types of seals are generally used, non-contact seals or contactseals. With non-contact seals (which do not contact the matrix face), itis a major challenge to properly adjust a gap between the matrix faceand the non-contact seal minimizing leakage to maximize efficiency ofthe heat exchanger. Contact seals (which do contact the matrix face)ensure lower leakage which improves efficiency of the regenerator ascompared to non-contact seals. Use of contact seals, however, causesincreased seal wear and also reduces efficiency of the regenerator dueto the increased function between the contact seal and the matrix thatmust be overcome in the rotation of the matrix. Additionally, rubbing ofthe contact seals on the regenerator matrix can over time produce solidmaterial (either from the matrix or the seals) which will contaminatethe flow and might lead to clogging in a porous matrix.

BRIEF DESCRIPTION OF THE INVENTION

The present invention solves the aforementioned problems by providing aregenerative heat exchanger including a brush-seal configuration toprevent mixing of fluid flows. The regenerative heat exchanger includesa regenerator matrix, and at least two conduits, each conduit having amatrix end abutting a face of the regenerator matrix. At least twoconduits carry at least two fluid flows which pass through theregenerator matrix. The regenerative heat exchanger includes a pluralityof brush-seals. Each brush-seal is located at a matrix end of eachconduit without contacting the matrix, thereby sealing around aperiphery of each conduit to prevent mixing of fluid flows.

A method for establishing a minimal gap between a regenerator matrix ofa regenerative heat exchanger and a plurality of brush-seals isdisclosed. The method includes installing the plurality of brush-sealssuch that a bristle end of each brush-seal contacts a face of theregenerator matrix. The regenerator matrix is rotated at a desired speedabout an axis substantially perpendicular to the face of the regeneratormatrix. During rotation, friction between the bristle end and the facecauses material to be removed from the bristle end. The rotation isstopped when a power required to rotate the regenerator matrix at thedesired speed reaches a predetermined level. This stops the removal ofmaterial from the bristle end and establishes a minimal gap between thebristle end and the face of the regenerator matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of preferred embodiments when considered in lightof the accompanying drawings in which:

FIG. 1 depicts an end view of an embodiment of a regenerative heatexchanger;

FIG. 2 depicts a cross-sectional view of the regenerative heat exchangerof FIG. 1; and

FIG. 3 depicts an enlarged view of the circled portion of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

Shown in FIG. 1 is an embodiment of a regenerative heat exchanger(regenerator) 10. Referring now to FIG. 2, the regenerator 10 includes aregenerator matrix 12. The matrix 12 generally comprises a body having aplurality of internal passageways (not shown) oriented in all axialdirection, and may be formed of a low-thermal-conductivity andhigh-heat-capacity material, for example, a ceramic material. In someembodiments, the matrix 12 may include an abradable coating layer (notshown) to protect the matrix 12 material from wear. The matrix 12 insome embodiments is cylindrical in shape, but other shapes arecontemplated within the scope of this invention. The matrix 12 isdisposed across two or more fluid streams. Each fluid stream is carriedin a conduit. In this embodiment, a cold fluid stream is carried in afirst conduit 14 and a hot fluid stream is carried in a second conduit16.

The matrix 12 is connected to a drive motor 18. The drive motor 18causes the matrix 12 to rotate about a matrix axis 20 and transfer heatfrom the hot fluid stream carried through second conduit 16 to the coldfluid stream carried through first conduit 14. Because the matrix 12moves relative to the first conduit 14 and the second conduit 16, aconfiguration of seals is required on a face 22 of the matrix 12 toprevent leakage, including leakage from the conduits 14 or 16, andleakage between the first conduit 14 and the second conduit 16.

Sealing between the face 22 and each of the conduits 14 and 16 isaccomplished by a brush-seal configuration 24. The brush-sealconfiguration 24 between first conduit 14 and the face 22 issubstantially identical to the brush-seal configuration 24 betweensecond conduit 16 and the face 22, so only the brush-seal configuration24 between first conduit 14 and the face 22 will be described herein.The brush-seal configuration 24 may be made from a variety of materialsincluding metal, super alloys, ceramics, etc., and is chosen dependingon thermal and chemical requirements of the application. As shown inFIG. 3, the brush-seal 24 extends around a periphery of the firstconduit 14 at the face 22, and is fixed to a seal holder 26 at a baseend 28 of the brush-seal 24 by a plurality of seal screws 30 or othermeans. In this example, the seal holder 26 has a U-shaped section 32 forreceiving brush-seal 24. A seal screw 30 is inserted though a screw hole(not shown) in the section 32 and threaded into a seal hole (not shown)securing the blush-seal 24 to the seal holder 26.

The seal holder 26 is secured to a casing 34 by a plurality of casingscrews 36. The casing 34 extends circumferentially around the firstconduit 14, and is fixed relative to the first conduit 14. The casingscrews 36 are inserted in a radial direction through axially-slottedholes 38 in the seal holder 26 and into threaded casing holes (notshown) in the casing 34, thereby securing the seal holder 26 to thecasing 34. The slotted holes 38 allow the position of the seal holder 26to be adjusted relative to the casing 34, and thus the position of thebrush-seal 24 relative to the face 22 can be adjusted. Initially, thebrush-seal 24 is positioned so the bristles 40 are in contact with theface 22. It is to be appreciated that the attachment scheme of theblush-seals 24 described herein is only an example. Other attachmentschemes including, for example, adhesive attachment, are contemplatedwithin the scope of this invention.

When the blush-seals 24 are installed, a break-in process is employed toestablish a minimal gap between the blush-seals 24 and the matrix 12 atthe faces 22. In one embodiment, a necessary power, P_(ref), forrotation of the matrix 12 at a desired rotation speed is determinedprior to installing the brush-seals 24. The brush-seals 24 are installedso the bristles 40 contact the matrix 12 as described above. The matrix12 is rotated to the desired rotation speed, and a power required torotate the matrix 12, P_(in), is monitored. Initially, because of thecontact between the bristles 40 and the matrix 12, P_(in)>P_(ref).During this break-in process, the regenerator 10 is run under normalwordings conditions, i.e. the flows passing through the regenerator willbe at the temperatures of the flows during normal operation. Thefriction between the bristles 40 and the matrix 12 during the break-inprocess increases the temperature of the bristles 40 and the matrix 12,and thus will cause slightly increased thermal expansion of the matrix12 and the bristles 40 over that which would occur during normaloperation.

As the break-in process progresses, material is worn off of the bristles40 and/or the face 22. As material is worn off, friction between thebristles 40 and the matrix 12 is reduced. Because of the reducedfriction, the temperature of bristles 40 and the matrix 12 are reducedslightly, reducing thermal expansion of the bristles 40 and the matrix12, thus creating a slight gap between the bristles 40 and the matrix12. The reduced friction also reduces P_(in) required for the matrix 12to rotate at the desired speed. P_(in) is monitored untilP_(in)=P_(ref), at which point the break-in process is completed,leaving the desired gap between the bristles 40 and the matrix 12.

While embodiments of the invention have been described above, it will beunderstood that those skilled in the art, both now and in the future,may make various improvements and enhancements which fall within thescope of the claims which follow. These claims should be construed tomaintain the proper protection for the invention first described.

1. A regenerative heat exchanger comprising: a regenerator matrix; atleast two conduits, each conduit having a matrix end abutting a face ofthe regenerator matrix, the at least two conduits carrying at least twofluid flows, the fluid flows passing through the regenerator matrix; anda plurality of brush-seals, each brush-seal disposed at a matrix end ofeach conduit without contacting the matrix, thereby sealing around aperiphery of each conduit to prevent mixing of fluid flows.
 2. Theregenerative heat exchanger of claim 1 wherein each brush-seal isaffixed to a casing.
 3. The regenerative heat exchanger of claim 2wherein the plurality of brush-seals is affixed to the casing by aplurality of screws.
 4. The regenerative heat exchanger of claim 3wherein each screw is installed through a slotted hole in the casing,allowing the position of the brush-seal to be adjusted.
 5. Theregenerative heat exchanger of claim 2 wherein the plurality ofbrush-seals is affixed to the casing by adhesive.
 6. The regenerativeheat exchanger of claim 1 wherein the regenerator matrix includes aplurality of axially-oriented internal passageways.
 7. The regenerativeheat exchanger of claim 1 wherein the regenerator matrix is formed of alow-thermal-conductivity and high--heat-capacity material.
 8. Theregenerative heat exchanger of claim 7 wherein the regenerator matrix isformed from a ceramic material.
 9. The regenerative heat exchanger ofclaim 1 wherein the regenerator matrix includes an abradable coatinglayer.
 10. The regenerative heat exchanger of claim 1 wherein eachbrush-seal is formed from a superalloy material.
 11. The regenerativeheat exchanger of claim 1 wherein each brush-seal is formed from aceramic material.
 12. A method for establishing a minimal gap between aregenerator matrix of a regenerative heat exchanger and a plurality ofbrush-seals, the brush-seals sealing around a periphery of each conduitof a plurality of conduits carrying fluid flows which pass thorough theregenerator matrix, the method comprising: installing the plurality ofbrush-seals such that a bristle end of each brush-seal contacts a faceof the regenerator matrix; rotating the regenerator matrix at a desiredspeed about an axis substantially perpendicular to the face of theregenerator matrix, friction between the bristle end and the facecausing material to be removed from the bristle end and/or the face ofthe regenerator matrix; stopping rotation of the regenerator matrix whena power required to rotate the regenerator matrix at the desired speedreaches a predetermined level, stopping the removal of material from thebristle end and/or the face of the regenerator matrix and establishing aminimal gap between the bristle end and the face of the regeneratormatrix.
 13. The method of claim 9 wherein the face of the regeneratormatrix includes an abradable coating layer.
 14. The method of claim 9wherein the temperatures of the flows passing through the regeneratorare substantially the same as at normal operation of the regenerativeheat exchanger.
 15. The method of claim 9 wherein the power iscontinuously monitored to determine when the power reaches thepredetermined level.
 16. The regenerative heat exchanger of claim 9wherein the regenerator matrix is formed from a ceramic material. 17.The regenerative heat exchanger of claim 9 wherein each brush-seal isformed from a superalloy material.
 18. The regenerative heat exchangerof claim 9 wherein each brush-seal is formed from a ceramic material.